This invention relates to a novel process for producing alkenyl-aromatic hydrocarbon derivatives.
Because of their excellent solubility, aromatic compounds such as benzene, toluene, xylene and the like have heretofore been used widely as solvents for rubbers, synthetic resins, paints, agricultural chemicals such as pesticides, resin treatment of fibers, cleaning of metal parts, releasants for paints, printing ink, etc.
According to their utility, they must have a high boiling point in view of evaporation loss, safety, toxicity, evaporation rate, etc.
In order to increase the boiling point of aromatic compounds, it is known to introduce an alkyl group in an aromatic compound to form an alkyl-aromatic compound.
the introduction of an alkyl group leads to a decrease in solubility although it results in an increase in the boiling point of the resulting compound. It is often the case that the product isn't used insufficiently as a solvent depending on the purposes for which it is employed. Polychlorinated biphenyl, a typical example of a high boiling point aromatic compound, that was widely used as a heat transfer oil, an electric insulating oil, a solvent for pressure-sensitive paper, a plasticizer for rubbers and various synthetic resins, etc., have recently not been used because it has a high toxicity to humans and pollutes environment seriously. Therefore, high boiling aromatic compounds which are free of problem of environmental pollution are desired.
The alkenyl-aromatic hydrocarbon derivatives produced according to the process of this invention meet the above demand. Further, hydrogenated derivatives thereof are useful as traction drive oil.
Conventionally, alkenyl-aromatic hydrocarbon derivatives have been produced from an aromatic hydrocarbon and an alkenyl-aromatic hydrocarbon by (1) a process using a sulfuric acid having a concentration of 80 to 99% as a catalyst as described in Japanese Patent Publication No. 55-50929, or (2) a process using silica-alumina, acidic clay, zeolite exchanged for proton or a metal cation, or a strongly acidic cation exchange resin as described in Japanese Patent Publication No. 55-33692 as a catalyst.
However, those processes using sulfuric acid as a catalyst as process (1) above are disadvantageous in corrosion of apparatus due to sulfuric acid, additional steps for removal of sulfuric acid from the reaction mixture, neutralization with an alkali and washing with water long time for drying and disposing waste sulfuric acid.
Further, those processes using a solid catalyst such as a strongly acidic cation exchange resin as process (2) above, cause problems that the reaction mixture is acidic. And it is necessary to provide a step of neutralizing the mixture and the catalyst used cannot be regenerated for reuse since the catalyst is deactivated considerably during the reaction.
Moreover, solid catalysts are disadvantages in lower activity, they need a long reaction time, and yield and selectivity of a desired alkenyl-aromatic hydrocarbon are low.
As stated above, the conventional processes are not satisfactory as a process for producing alkenyl-aromatic hydrocarbon derivatives on an industrial scale.